Electric Eel‐Inspired Elastomer‐Encapsulated Hydrogel Sensor with Superior Anti‐Swelling, Self‐Adhesion, and Electrical Stability for Diverse Underwater Applications

Abstract Developing reliable underwater flexible sensing materials is a highly focused research topic, but challenges such as insufficient environmental stability and signal attenuation still remain. In this work, an electric eel‐inspired encapsulation structure is proposed, consisting of a hydroxyl‐rich conductive hydrogel (SNA) core and a hydrophobic insulating elastomer (HPC) shell, with encapsulation achieved through in situ polymerization by embedding wires. The SNA‐HPC gel sensor demonstrates excellent signal stability (no signal attenuation during water entry and exit, over 3000 cycles of testing), ultra‐high underwater sensitivity and conductivity (GF = 1.997, σ = 0.51), and outstanding self‐adhesion (143.1 kPa in air/91.3 kPa underwater). Moreover, the interfacial bonding strength between SNA and HPC reaches 243.63 N m⁻¹. SNA‐HPC is successfully applied in deep‐learning‐assisted swim posture recognition, Morse code‐based underwater communication, and multi‐scenario human‐machine interaction through the SNA∗n‐HPC matrix sensor. This work is expected to provide insights into the development of high‐quality underwater wearable electronic devices and the multifunctionalization of underwater sensing.